This application provides a physical downlink control channel processing method and a related device. In the method, a search space may be determined based on a first radio network temporary identifier, where the search space is a set of M candidate physical downlink control channels; and a target physical downlink control channel is detected from the search space based on a second radio network temporary identifier, where the first radio network temporary identifier is a radio network temporary identifier of a first device or a second device, the second radio network temporary identifier is the radio network temporary identifier of the second device, first downlink control information carried by the target physical downlink control channel is information that is scrambled by using the second radio network temporary identifier and that is used to schedule the second device, and the second device communicates with a network by using the first device.